With an increasing need for lightweight automobiles to improve their fuel efficiency, resin components have replaced metal components. Resin components have various advantages such as high workability, low noise, and high plasticity in addition to light weight.
In order to further increase the advantage of plasticity, various techniques have been developed to produce various hollow components by joining primary molded parts by welding. Examples of such techniques include vibration welding, hot plate welding, ultrasonic welding, laser welding, and injection welding. In particular, injection welding has attracted attention because of its high productivity.
In order to increase the weld strength between the primary molded parts joined by injection welding, various polyamide-containing injection welding materials have been proposed. For example, Patent Literature 1 discloses that a polyamide composition containing an aromatic polyamide and an aliphatic polyamide mixed at a specific weight ratio can be used as an injection welding material. Patent Literature 2 discloses that a polyamide composition containing a polyamide, glass fiber, and a nigrosine compound can be used as an injection welding material. Patent Literature 3 discloses that a polyamide composition containing a crystalline polyamide having a specific terminal amino group concentration, an amorphous, partially aromatic copolyamide, and an inorganic filler can be used as an injection welding material. Patent Literature 4 discloses that a polyamide composition containing a polyamide having a specific terminal amino group concentration and a specific viscosity number and a fibrous reinforcing material can be used as an injection welding material. Patent Literature 5 discloses that a polyamide composition containing a specific copolyamide and an inorganic filler can be used as an injection welding material. However, when any of the injection welding materials described in these patent documents is used to weld primary molded parts, the weld strength between the primary molded parts needs to be further improved.